CMOS differential amplifiers are used in analog and digital circuits. A configuration of a CMOS operational amplifier includes a CMOS differential amplifier followed by an output stage. A CMOS differential amplifier without the output stage is usable, for example, in memory sense amplifiers. One example of a CMOS differential amplifier is a CMOS current mirror differential amplifier that includes a differential input circuit coupled to a current mirror load circuit.
The frequency and time responses of a CMOS amplifier are affected by the Miller effect. The gate-to-drain capacitance of an input transistor is amplified, by the voltage gain of the CMOS amplifier stage that the transistor is a part of, and is reflected back to the transistor input, i.e., the gate terminal of the input transistor. The frequency and time responses are determined by the amplified gate-to-drain capacitance, in addition to the gate-to-source capacitance, of the input transistor. The result significantly reduces frequency response and switching speed of the CMOS amplifier.
There is a need to improve the frequency and time responses of CMOS amplifiers.